Experiment of Holt and Pipkin

To produce the required radiation, mercury vapor was excited to the 9 Pi state by a 100-eV electron beam, both the beam and the vapor being 

In contrast to the two previous experiments, calcite-type polarizers were used with transmission efficiencies cmi = 0.910 0.001, m2 = 0.880 0.001, Emi, e 2 lO . This type of polarizer has a much better extinction ratio than pile-of-plates polarizers, but the values of Cmi and m2 are not particularly high. What is more, since a 1-1-0 cascade is being used, the factor F( ) takes on the relatively low value 0.951 even with an acceptance half-angle of only 13°. 

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